[php-src] Issue #24506: `stream_select()` leaks a stream-error operation level on its FD_SETSIZE failure path

Issue: https://github.com/php/php-src/issues/24506 Author: azjezz ### Description Each stream_select() call that hits the PHP_SAFE_MAX_FD check (any fd >= FD_SETSIZE, 1024 on macOS and Linux) emits its "You MUST recompile PHP with a larger value of FD_SETSIZE" warning and returns false. It also leaves one operation level open. After 1,000 such calls, **every later stream operation in the process** (fread, fwrite, ..etc) emits: ``` Warning: fread(): Stream error operation depth exceeded (1000), possible infinite recursion ``` The operation itself still succeeds. The warnings never stop until the process exits. Example: ```php $keep = []; while (true) { // open sockets until one has fd >= 1024 $p = stream_socket_pair(STREAM_PF_UNIX, STREAM_SOCK_STREAM, 0); $keep[] = $p; if (count($keep) * 2 > 1100) { break; } } [$hi] = end($keep); [$a, $b] = stream_socket_pair(STREAM_PF_UNIX, STREAM_SOCK_STREAM, 0); $calls = (int) ($argv[1] ?? 1001); for ($i = 0; $i < $calls; $i++) { $r = [$hi]; $w = $e = null; @stream_select($r, $w, $e, 0); } fwrite($b, 'x'); $last = null; set_error_handler(function ($no, $str) use (&$last) { $last = $str; return true; }); $data = fread($a, 1); restore_error_handler(); printf("after %d over-limit stream_select() calls: fread()=%s warning=%s\n", $calls, var_export($data, true), $last ?? 'none'); ``` ```sh ulimit -n 4096 php reproduce.php 2000 # 8.6.0RC3: warning=fread(): Stream error operation depth exceeded (1000)... php reproduce.php 999 # no warning ``` On 8.5.4 the same script prints warning=none. ### PHP Version ```plain PHP 8.5.4 (cli) (built: Mar 31 2026 17:40:26) (NTS) Copyright (c) The PHP Group Zend Engine v4.5.4, Copyright (c) Zend Technologies with Zend OPcache v8.5.4, Copyright (c), by Zend Technologies ``` ### Operating System MacOS